The value field shall contain a character string
giving
the name of parametern. If the PTYPEn
keywords for more than one value of n have the same associated
name in the value field, then the data value for the parameter
of that name is to be obtained by adding the derived data values
of the corresponding parameters. This rule provides a mechanism by
which a random parameter may have more precision than the
accompanying data array elements; for example, by summing two 16-bit
values with the first scaled relative to the other such that the
sum forms a number of up to 32-bit precision.

This keyword shall be used, along
with the PZEROn
keyword, when the nthFITS group parameter
value is not the true
physical value, to transform the
group parameter value to the true physical values it represents,
using Eq. 7.2.
The value field shall contain a floating point number representing
the coefficient of the linear term in Eq. 7.2, the scaling
factor between true values and group parameter values
at zero offset. The default value for this keyword is 1.0.

This keyword shall be used, along
with the PSCALn keyword, when
the nthFITS group parameter
value is not the true physical
value, to transform the group parameter value to the physical value.
The value field shall contain a floating point number,
representing the true value corresponding to a group
parameter value of zero. The default value for this keyword is 0.0.
The transformation equation is as follows: